Australia's immigration minister has described refugees as "illiterate and innumerate" people who would both "take Australian jobs" and "languish" in unemployment — comments swiftly denounced as xenophobic and offensive by opponents but backed by the country's prime minister.

The assertions by Peter Dutton brought border security and immigration firmly to the center of the 2016 election campaign, which has become closer than his ruling Liberal-Nationals Coalition had hoped.

Asked about opposition plans to increase the country's intake quota of refugees, Dutton told Sky News: "For many people, they won't be numerate or literate in their own language, let alone English... these people would be taking Australian jobs, there's no question about that, and for many of them that would be unemployed they would languish in unemployment queues and on Medicare and the rest of it."

Border security and immigration are hot political issues in Australia that have swayed past elections and resulted in a bipartisan hardline policy under which all asylum seekers arriving by boat are sent to South Pacific island detention camps in tiny Nauru and Papua New Guinea (PNG), and are deemed ineligible for resettlement. The policy contravenes international law and the offshore camps have been internationally condemned for their harsh conditions and the mental trauma inflicted on those held there indefinitely.

Australia's immigration minister has described refugees as "illiterate and innumerate" people who would both "take Australian jobs" and "languish" in unemployment — comments swiftly denounced as xenophobic and offensive by opponents but backed by the country's prime minister.

The assertions by Peter Dutton brought border security and immigration firmly to the center of the 2016 election campaign, which has become closer than his ruling Liberal-Nationals Coalition had hoped.

Asked about opposition plans to increase the country's intake quota of refugees, Dutton told Sky News: "For many people, they won't be numerate or literate in their own language, let alone English... these people would be taking Australian jobs, there's no question about that, and for many of them that would be unemployed they would languish in unemployment queues and on Medicare and the rest of it."

Border security and immigration are hot political issues in Australia that have swayed past elections and resulted in a bipartisan hardline policy under which all asylum seekers arriving by boat are sent to South Pacific island detention camps in tiny Nauru and Papua New Guinea (PNG), and are deemed ineligible for resettlement. The policy contravenes international law and the offshore camps have been internationally condemned for their harsh conditions and the mental trauma inflicted on those held there indefinitely.

Dutton's assertions came just before a major investigation into the impact refugees have on host communities was published, which found while they require initial investment, they yield economic benefits worth double the amount within five years. The study — which used International Monetary Fund data and was written by former economic adviser to the president of the European Commission Philippe Legrain for the NGO Tent Foundation — found that refugees create jobs, fill gaps in the labor market, and boost innovation.

It also noted that the only developed country where studies have attempted to measure refugees' overall economic impact is Australia — and all have found that refugees net contribution is positive. A fact-check article published by the Guardian on Wednesday noted that a 2011 report by Australia's Department of Social Services found more than three quarters of refugees in Australia were literate and educated to high school level before arrival.

Australia's conservative government last year pledged to take 12,000 refugees from Syria on top of its 13,750 annual quota, made up of people who are granted asylum after making applications from outside the country. The center-left opposition Labor Party backs the policy of sending all asylum seekers arriving by boat to offshore detention centers, but says it will double the annual quota to 27,000 by 2025 if it wins elections on July 2.

Prime Minister Malcolm Turnbull is seeking to portray the opposition as weak on border security.

Dutton's comments were swiftly berated by Labor and the small left-wing opposition Greens Party, which is arguing for the intake quota to be increased to 50,000 people.

Labor leader Bill Shorten blasted Dutton for making "deeply divisive and offensive" statements that had lowered the tone of the election, while Greens Senator Sarah Hanson-Young called the comments "xenophobic."

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"Mr. Dutton didn't just insult refugees when he made those comments. He insulted the millions of migrants who've contributed to making this a truly great country," Shorten told reporters.

He demanded Turnbull condemn the remarks but the leader declined to do so, instead defending his "outstanding immigration minister."

Refugees coming to Australia were often "from dreadful, devastated, war-torn regions of the world and many of them, large percentages of them, have no English skills at all. Many of them are illiterate in their own language. Many haven't completed high school," said Turnbull.

"That's no fault of theirs. That's why we're reaching out to help them with compassion. That is not a basis for criticizing them."

Behnam Satah, a 30-year-old asylum seeker detained on Manus Island in PNG, said many in the camp were well educated and would be a boon to the Australian economy.

"If one day we go to Australia, history will prove this. And that day I will go to [Dutton] and say: 'What do you say now?'" said Satah, who was studying a Master's degree in English Education before fleeing his native Iran.

Paul Power, from the Refugee Council of Australia, said Dutton's comments were incoherent nonsense that contradicted the evidence provided by hundreds of thousands of refugees who had contributed to Australian society. "The fact that this political attack is coming from the minister responsible for Australia's refugee program makes it even more offensive," he told the Sydney Morning Herald.

An Afghani co-owner of a fruit farm in the southeast of the country worth $10 million Australian dollars ($7.2 million), who arrived from Nauru as an illiterate refugee 12 years ago, defended the work ethic of refugees.

"When they come here they have to work hard, otherwise they won't be able to afford a house and do the things they want to do for their families," he told Fairfax Media.

The Nauru and Manus Island camps have made international headlines in recent weeks. The PNG government declared the Manus camp illegal and ordered its closure in April, while two asylum seekers have set themselves on fire in protest against their treatment on Nauru.

One of them, a 23-year-old Iranian man who was a recognized refugee, died two days later. Before his death, his wife criticized inadequate medical facilities in Nauru and delays in getting him to a proper hospital in comments made to the Guardian.

Dutton has blamed refugee advocates for encouraging asylum-seekers to self-harm in the mistaken belief it will help them get to Australia or influence the government to change its policy.

More than 900 people are detained on Manus Island on Australia's behalf, while the detention center on Nauru holds about 500 people, including 70 children.

Both have been widely criticized by the United Nations and human rights agencies for harsh conditions and reports of widespread assault, sexual violence, and systemic child abuse. They are off-limits to journalists.